Bibulous cellulosic fibers

ABSTRACT

Bibulous cellulosic fibers for use in fibrous structures having an inherently absorptive function, for example surgical dressings, surgical sponges filters, catamenial napkins, tampons and diapers, which bibulous cellulosic fibers, and fibrous structures containing said bibulous fibers in effective amounts, are characterized by greatly improved absorbency for and retention of aqueous solutions, including physiological solutions. The bibulous cellulosic fibers are substantially water-insoluble, wet cross-linked fibrous salts of carboxymethyl cellulose having a sufficiently high degree of carboxymethyl substitution to insure water solubility in the absence of crosslinking. The bibulous cellulosic fibers are produced under conditions which preserve the fibrous form of the cellulose fiber raw material.

- Unite 1' States Patent [73] Assignee The Buckeye Cellulose CorporationCincinnati, Ohio Continuationin-part of application Ser. No. 713,143,Apr. 14, 1968, now abandoned.

[54} BIBULOUS CELLULOSIC FIBERS 3,005,456 10 1961 Graham,Jr 1. 128/2853,069,311 12/1962 Harphametal. .1 162/146 3,070,095 12/1962 Torr 128 2843,241,553 3/1966 Steiger 128/156 3,339,550 9 1967 VanHaaften., 128 2903,386,231 6/1968 Nutting 162 146 3,423,167 1/1969 Kuzmaketal. 8/129FOREIGN PATENTS 632,111 12 1961 Canada 128/287 Primary ExaminerCharlesF. Rosenbaum Attorneys-William S. Shelow, Ill and Richard C. WitteABSTRACT: Bibulous cellulosic fibers for use in fibrous structureshaving an inherently absorptive function, for exam- 10 Claims, 2 DrawingFigs.

I ple surg1cal dressmgs, surgical sponges filters, catamemal nap- U.S.kins tampgns and diapers bibulous cellulosic fibers 8/l 128/2851128/2901 128/296 162/146 and fibrous structures containing said bibulousfibers in effec- [51] Int. Cl A6lf 13/16 fi e amounts, are characterizedby greatly improved b [50] Field oi Search 162/146, bency f andretention f aqueous Solutions, including 3/ 1 284235, 1 physiologicalsolutions. The bibulous cellulosic fibers are sub- 1 296 stantiallywater-insoluble, wet cross-linked fibrous salts of carbox methylcellulose having a sufficiently high degree of car- [56] References Cmboximethyl substitution to insure water solubility in the UNITEDSTATES/PATENTS absence of cross-linking. The bibulous cellulosic fibersare 2,486,805 1 [/1949 Seymour et al, 128/287 produced under conditionswhich preserve the fibrous form of 2,971,815 2/1961 Bullock et al 8/116.2 the cellulose fiber raw material.

WRV/IOO DEX XI D'Ex 11 l l I O 0.2 0.4 0.6 0.8 L0 1.2 L4 L6 L8Corboxymethyl DS PATENTEDJUNZQIQ?! 3,589,364

SHEET 1 [IF 2 Fig. l WRV/IOO 'Ex XI EPEx E Ex EIL D*Ex m {PEX m 0 l I ll l l l 0 0.2 0.4 0.6 0.8 L0 L2 L4 L6 L8 Curboxymethyl DS INV/iNlURSWalter L. Deon George N. Ferguson W 5. inky ATTORNEY Pmimmuuzslsn$589,364

SHEET 2 [1F 2 Fig. 2

SRV/IOO 'ExX III l l l O 0.2 0.4 0.6 0.8 L0 L2 L4 L6 L8 Corboxymethyl DSINVISN'I'URS Walter L. Deon George N. Ferguson pm? S22 1 A T TORNEYBIBULOUS CELLULOSIC FIBERS This application is a continuation-in-part ofcopending application, Ser. No. 713,143, filed Mar. 14, 1968 nowabandoned.

BACKGROUND OF THE INVENTION This invention relates to the production ofbibulous cellulosic fibers by chemically modifying cellulosic fibers toproduce wet cross-linked and etherified cellulosic fibers which aresubstantially water-insoluble and manifest their original fibrousstructure. More particularly, the invention relates to the provision ofsubstantially water-insoluble, wet cross-linked fibrous salts ofcarboxymethyl' cellulose which display improved absorbency and retentioncharacteristics for aqueous solutions, including physiologicalsolutions, and impart these characteristics to fibrous structures inwhich they are included.

Specifically, the invention, in one of its more important embodiments,consists of wet cross-linked fibrous salts of carbox' ymethyl cellulosewhich display their original cellulosic fibrous form and have asufficiently high degree of substitution (DS) to be normallywater-soluble, which fibrous salts of carboxymethyl cellulose have beenwet cross-linked to achieve substantial water insolubility. Suchsubstantially water-insoluble, wet cross-linked carboxymethyl cellulosefibers, sometimes referred to hereinafter as bibulous fibers forconciseness, are particularly adapted by their unique intrafiberabsorbency for and retention of aqueous solutions for either use oradmixture in effective amount in fibrous structures, including surgicaldressing, surgical sponges, filters, catamenial napkins, tampons anddiapers containing in effective amount the substantiallywater-insoluble, wet cross-linked carboxymethyl cellulose fibers of thisinvention. The disclosed bibulous fibers also exhibit a particular andunique absorbent affinity for dilute aqueous solutions of salts andother physiological solu tions. In addition, the disclosed bibulousfibers exhibit the capability of absorbing and retaining virtually allof the undissolved water from substantially immiscible aqueous systemscomprised of water together with at least one hydrocarbon such aschloroform, gasoline, benzene, toluene, kerosene, xylene, pentane,hexane, cyclohexane, and longer chain length saturated and unsaturatedhydrocarbons of this type.

Several papermaking techniques and fiber selections intended to resultin absorbent fibers, fibrous structures, waddings, nonwovens and papershave been developed and used heretofore. For example, the commercialgrades of absorbent papers designated as blotting papers, filter papers,paper towelings and sanitary tissues are, in general, charac' terized bybeing produced in a soft, loosely felted condition to maximizeabsorbency. Such absorbent papers are generally unsized and are alsooften accorded a creping or other mechanical treatment after drying tofurther enhance and increase subjective softness and absorbency. Theindividual fibers from which such absorbent papers are produced arecarefully selected for their contribution to the absorbencycharacteristics of such papers. Such individual fibers can be and areselected from rag fibers, high alpha wood and cotton linter fibers,ground wood fibers and mixtures thereof, and minor amounts of otherfibers, for example crimped staple rayon fibers, can be incorporated toenhance structure. Further, such selected fibers in a furnish forproducing absorbent papers are usually beaten lightly, if at all, tomaximize the absorbency characteristics of the resulting papers, waddingand felted products.

Paperrnaking fibers, specifically cotton linter fibers and woodpulpfibers, have further been cross-linked without etherification prior totheir inclusion in papermaking furnishes according to the teaching ofU.S. Pat. No, 3,069,311 1, issued to John A. Harpham and Harry W. Turneron Dec. 18, 1962. Also, US. Pat. No. 3,241,553, issued to Fred H.Steiger on Mar. 22, 1966, discloses the cross-linking of cellulosicfibers, including cotton, wood pulp, cotton linter and regeneratedcellulosic fibers, while they are in a wet swollen condition, to improvethe fluid absorbency and fluid retention characteristics of fibrousstructures from such fibers for body fluids. Cotton fabrics and fabricswoven of other cellulosic fibers, for example rayon and celluloseacetate, have also been accorded a measure of crease resistance bytreatments with both a polyfunctional agent for cross-linking, forexample epichlorohydrin and formaldehyde, and a monofunctional agent foreither of etherification or esterification, for example monochloroaceticacid as disclosed in US. Pat. No. 2,971 ,815, issued to Austin L.Bullock and John D. Guthrie on Feb. 14, 1961.

Applicants have found, however, that the absorbency and retentioncharacteristics of ccllulosic fibers for aqueous solutions, includingphysiological solutions, can be greatly improved, i.e., about threetimes to in excess of about 20 times improved, over such characteristicsof fibers produced according to teachingsand suggestions previouslyavailable in the art. Such large scale improvements are generallyrealized, according to applicants present disclosure, by convertingcellulosic fibers into fibrous salts of carboxymethyl cellulose having adegree of substitution (DS) sufficient to insure water solubility in theabsence of cross-linking. The carboxymethylation is accomplished eitherin an organic liquid media slurry process or in a so-called doughprocess which preserves the original fibrous form of the cellulose. Theresulting carboxymethylated cellulosic fibers are then wet crosslinkedto insure substantial water insolubility and retention of fibrous formin use. Applicants point. out, however, that the order of performance ofthe carboxymethylation and wet cross-linking steps, whereby the bibulousfibers are produced, is not critical, and initial wet cross-linkingfollowed by carboxymethylation or simultaneous performance of the twosteps of carboxymethylation and wet cross-lining is within the purviewof the present invention.

SUMMARY OF THE INVENTION Inasmuch as fibers having increased absorbencyand retention capacities for aqueous solutions, including physiologicalsolutions, were desired for use in various types of fibrous structures,applicants further investigated their discovery that certain wetcross-linked cellulose derivative fibers exhibited the stated bibulouscharacteristics to an astonishingly high degree. Applicantsinvestigation revealed that the unusually absorbent and retentive fiberscan be prepared by carboxymethylating native and regenerated cellulosicfibers to a D8 which normally assures water solubility while preservingtheir initial fibrous form. The resulting fibrous sodium carboxymethylcellulose is then wet cross-linked to produce the instant bibulousfibers. Wet cross-linking in the present instance comprises the step oftreating fibrous salts of carboxymethyl cellulose, swollen with at leastminor amounts of water, with a reagent polyfunctional with respect tocellulose, for example epichlorohydrin.

Although the wet crosslinking of unmodified cellulose fiber is known toresult in about a two-fold improvement in the absorbency of fibrousstructures, applicants were surprised to discover that the presentbibulous fibers having a D5 of about 0.4 to about 16, preferably about0.6 to about 1.2, exhibited a manyfold increase in intrafiber absorbencyand retention. Applicants were further surprised to discover that asminimum values increased over the minimum required DS to insure watersolubility in a cellulosic fiber without wet cross-linking according tothe instant invention, there existed a range of substantiallywater-insoluble wet cross-linked fibrous carboxymethyl products, at a D5of about 0.6 to about 1.6, which exhibited a particularly effectiveabsorbency and retention of water, dilute salt and other physiologicalsolutions.

It is, accordingly, a principal object of this invention to provide wetcross-linked fibrous salts of carboxymethyl cellulose which exhibitsuperior absorbency and retention characteristics with respect to waterand aqueous solutions, including physiological solutions.

It is, accordingly, a principal object of this invention to provide wetcross-linked fibrous salts of carboxymethyl cellulose which exhibitsuperior absorbency and retention characteristics with respect to waterand aqueous solutions, including physiological solutions.

It is a further object of the present invention to provide bibulousfibers for inclusion in papermaking furnishes, air-laid and water-laidnonwoven fabrics and in other fibrous pads and bandages whether they beof paper, woven or nonwoven origin.

It is yet another object of the present invention to provide wetcross-linked substantially water-insoluble fibers of carboxymethylcellulose, having a DS sufficiently high to insure water solubility inthe absence of wet cross-linking, for inclusion in the fibrous structureof a catamenial tampon having a substantially higher in-usc absorptivecapacity than that of prior art devices, which catamenial tamponprovides increased protection and wearing time.

It is also an object of this invention to provide catamenial tampons,surgical dressings and other absorbent pads and fibrous structureseither prepared from bibulous fibers or containing bibulous fibers inadmixture with other fibers.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantageousfeatures of the present invention will become apparent as the followingdescription of the instant bibulous fiber product, together with methodsfor its production and examples of its advantageous inclusion in usefulfibrous structures, proceeds apaee in this specification, as illustratedin part by the accompanying drawings wherein:

FIG. I is a graph which relates the D5 of examples of the present wetcross-linked fibrous carboxymethyl cellulose fibers to their intrafiberabsorbency as measured by Water Retention Value (WRV);

FIG. 2 is a graph which relates the D5 of examples of the present wetcross-linked fibrous carboxymethyl cellulose fibers to their intrafiberabsorbency as measured by Salt Water Retention Value (SRV).

The pertinent values of comparative fibers are also plotted on FIGS. land 2 in order to illustrate the high degree of absorbency exhibited bythe present bibulous fibers in comparison with other fibers.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In general, applicants havefound that the foregoing objectives can be met, as before stated, bypreparing a water-soluble salt of carboxymethyl cellulose having a D5 ofabout 0.4 to about 1.6, preferably about 0.6 to about 1.2, which retainsthe fibrous form of the original cellulose raw material with prior,concommitant or subsequent introduction of sufficient intrafibercross-links into the wet or swollen form of said fibrous water-solublesalt of carboxymethyl cellulose to insure sub stantial waterinsolubility. Such substantially water-insoluble, wet cross-linkedcarboxymethyl cellulose fibers exhibit a WRV of about 900 to about 3,400and a SRV of about 400 to about 1,500 in the stated DS range of about0.4 to about 1.6. In the preferred DS range WRVs of about 1,100 to about3,400 and SRVs of about 400 to about 1,500 are achieved. Fibrous saltsof water-soluble carboxymethyl cellulose having DSs in excess of about1.6 can be used, although, as a practical matter, the increasedabsorbency gained through the use of such high DS material is difficultto justify versus the increased chemical costs for etherification andcross-linking. Potassium sodium and lithium salts of fibrouswater-soluble carboxymethyl cellulose are suitable for wet cross-linkingin practicing the present invention; and, although the invention willhereinafter be illustrated in terms of fibrous water-soluble salts ofsodium carboxymethyl cellulose (NaCMC), it will be appreciated andunderstood that other fibrous water-soluble salts of carboxymethylcellulose, for example ammonium salts of fibrous water-solublecarboxymethyl cellulose, can be employeci. The necessary wet cross-linkscan be introduced into water swollen fibrous NaCMC by treatment with asuitable cellulosic cross-linking reagent, selected from the groupenumerated hereinbelow, but preferably epichlorohydrin. Suitablecellulosic fibers for carboxymethylation and wet crosslinking to formthe present bibulous fibers are cotton, wood pulp and rayon fibers,although lesser used cellulosic fibers, for example cellulosic fibersattained from straw, esparto grass, bagasse and other cellulosic fiberswill be found to increase in absorbency.

The minimum degree of substitution of about 0.4 required to assure watersolubility in the fibrous NaCMC prior to wet cross-linking to achievesubstantial water insolubility is obtainable by operation of the semidryprocesses disclosed in such patents as U.S. Pat. No. 2,510,355, issuedto William F. Waldeck on June 6, 1950 and U.S. Pat. No. 2,553,725,issued to Linwood N. Rogers, William A. Mueller and Ernest E. Hcmbree onMay 22, 1951, but preparation of the fibrous NaCMC of the hereindisclosed DS for cross-linking is readily accomplished by operation ofany of these socalled slurry processes for the manufacture of NaCMC, forexample the slurry process taught in U.S. Pat. No. 3,345,855, issued toRussell Nelson on Oct. 17, I967. Such slurry processes have theadvantage, in the preparation of the instant bibulous fibers, that theycan be easily controlled and operated to produce NaCMC having a DS inthe range of about 0.4 to about 1.6 and in the preferred range of about0.6 to about 1.2 in the fibrous form of the original cellulose rawmaterial as required for production of the fibrous wet cross-linkedNaCMC product of the present invention. The production of NaCMC fibershaving DSs of less than about 0.8 can be accomplished in oneetherification stage, but the achievement of DS's in excess of about 0.8is more easily accomplished and controlled by the use of at least twoetherification stages.

The fibrous water-soluble NaCMC with D5 of about 0.4 to about 1.6 isthen treated in the wet or swollen state with a suitable cellulosiccross-linking agent to introduce, engender or cause sufficientintrafiber cross-links to be formed so that the fibrous NaCMC becomessubstantially insoluble in water. It is also possible to reduce thewater solubility of bibulous fibers for particular applications byextracting crude bibulous fiber products with water prior to their useas fibers or admixture fibers in fibrous products. Suitablecross-linking reagents for use in producing the water-insolubleintrafiber crosslinked NaCMC product are, for example, epichlorohydrinand formaldehyde, and the type and amount of intrafiber crosslinking isderived from an amount of cross-linking agent sufficient to provideabout one cross-link per about six to about l9 anhydroglucose units,with the cross-links having been introduced into the cellulose orcellulose derivative while it is in the wet state. In the practice ofthe invention with epichlorohydrin, for example, the requiredcross-linking is accomplished by reaction with about 3 percent to about10 percent preferably about 3 percent to about 7 percent, by weight ofepichlorohydrin based on the dry weight of the original cellulose fiber.

Although the general preparation of the bibulous crosslinkedcarboxymethyl cellulose fibers of the present invention has beendescribed above in terms of preparing NaCMC of the prescribed DS andthen introducing sufficient wet cross-links to insure substantial waterinsolubility, it is to be understood that the wet cross-linking and theone or more etherification steps can be carried out in any order orconcomitantly. Appli cants have found that cross-linking wet cellulosefibers to form wet cross-linked cellulose prior to one or more stages ofetherification to obtain a desired DS has some materials handlingadvantages, although simultaneous etherification and wet cross-linkingoffers some economies in equipment and chemical usage.

As stated before, the bibulous fibers of the present invention aresubstantially water-insoluble. In practice, applicants have found thatbibulous fibers having water solubilities of less than about 30 percentdo not inhibit the penetration of liquid into fibrous structures inwhich they are present and do not interfere with the increased totalabsorbency of such structures.

Actually, the present bibulous fibers would be found almost totallyinsoluble if the etherification and wet cross-linking reactions werehomogeneous in nature. In practice, however, cellulosic fibers havingvarying degrees of polymerization enter into the wet cross-linking andetherification reactions, so that a degree of heterogeneity togetherwith some solubility results in the resulting bibulous fibers. Inapplications of the bibulous fibers where essentially water'insolublefibers are desired, it is possible to remove water-soluble fractionsfrom the bibulous fibers by extraction with water prior to use.

Referring now to FIG. 1 of the accompanying drawings, which graphicallyrelates to the carboxymethyl D5 of fibrous NaCMC wet cross-linked tosubstantial water insolubility with epichlorohydrin to fiber absorbencyin terms of the Water Retention Value/I (WRV/100) as defined below,applicants have discovered that the ability of wet cross-linked NaCMCfibers to retain water is greatly improved as the D8 of the cross-linkedNaCMC exceeds about 0.4. The graph points are identified as bibulousfibers in the following examples. Higher DSs up to about l.6 are alsoshown to be related to desirable and increased WRV values. Applicantsfurther prefer to produce the present bibulous fibers by wetcross-linking NaCMC fibers having a D of about 0.6 to about 1.2 becausethey have found, as illustrated by the graphed values of FIG. I, thatbibulous fibers in this DS range achieve the most advantage in increasedabsorbency versus production difficulties and chemical economies.

The graph points for illustrations 1, 2 and 3 are respectively theabsorbency results for wood pulp fibers with no carboxymethylation(DS=0), wet cross-linked wood pulp fibers with no carboxymethylation,and wet cross-linked NaCMC fibers with a DS of 0.14. The inclusion ofthese illustrations in FIG. 1 serves to illustrate the large increase inabsorbency achieved in the present bibulous fibers over previousabsorbent fibers. In FIG. 1 the upper solid line represents the curvefor bibulous fiber examples having a lower epichlorohydrin treatment ofabout 3 percent while the lower dotted line represents the curve forbibulous fiber examples having an epichlorohydrin treatment of about 5percent. The area between the two lines encompasses advantageousbibulous fiber products, and increased amounts of epichlorohydrintreatment, as stated before, will result in only a slight downwarddisplacement of the dotted line.

In a manner similar to the graphical illustration of FIG. 1, FIG. 2graphically relates the carboxymethyl D8 of fibrous NaCMC wetcross-linked to substantial water insolubility with epichlorohydrin toits fiber absorbency in terms of the Salt Water Retention Value/I00(SRV/IOO), as defined below. Illustrations 1, 2 and 3 are included forcomparison as in FIG. I, and it is noted that an aqueous solutioncontaining 1 percent by weight of salt displays absorbent propertiessimilar to physiological solutions such as urine, menstrual blood andblood.

As previously stated, the necessary wet cross-linking of the NaCMCfibers in the disclosed range of DS is accomplished by treatment of thefibrous NaCMC with a cross-linking reagent. Suitable cross-linkingreagents for use in preparing the present fibers are, for example,bis-epoxypropyl ether, dichloroethane, divinyl sulfone, epichlorohydrin,ethylene glycol-bis-epoxypropyl ether, formaldehyde, vinyl cyclohexenedioxide, l,3-dichloro-2-propanol, l,3-di(B-hydroxy-F-chloropropoxy)-2-propanol, l,2-di( B-hydroxy-F- chloropropoxy)ethane,l,2:3,4-diepoxybutane, I ,2:5,6- diepoxyhexane, 2,3-dibromo-l-propanol,2,3-dichloro-lpropanol and 2,2'-dichloroethyl ether, although other reagents polyfunctional with respect to cellulose can be em ployed. All ofthe cross-linking reagents listed above, with the exception offormaldehyde which requires acidic conditions, will cross-linkcarboxymethyl cellulose under alkaline conditions and result incross-links containing at least one carbon atom.

Applicants prefer epichlorohydrin for wet cross-linking in forming thepresent bibulous fibers because both the wet cross-linking andetherification can be simultaneously accomplished in a single alkalinemedium. The wet cross-linking necessary to result in substantial waterinsolubility can result from the treatment of NaCMC fibers, slurried ininert organic diluent and swollen in the presence of minor but swellingamounts of water, with about 3 percent to about 10 percent, preferablyabout 3 percent to about 7 percent, based on the weight of the originalcellulose in the NaCMC of epichlorohydrin under alkaline conditions forabout 24 hours at a temperature of about 25 C. Formaldehydecross-linking can e accomplished by treating swollen fibrous NaCMCfibers under acidic conditions with a dilute aqueous solution offormaldehyde.

Cross-linking of the cellulose raw material in its original fibrous andunmodified form can be accomplished by the foregoing treatment withepichlorohydrin or formaldehyde, and this treatment can be followed byetherification to result in the present bibulous fibers. Altemately,simultaneous crosslinking and etherification is, in general and forexample, carried out by treating water-swollen cellulose fibers withepichlorohydrin and with monochloroacetic acid in the presence of aslight excess of sodium hydroxide in an inert organic diluent or slurrymedium. Other carboxymethylating agents known in the art can be used toeffect the required etherification.

In describing the characteristics of the bibulous fibers which are thesubject of the present application, applicants have used several testingprocedures. Included in these testing procedures are the determinationof the Degree of Substitution (DS), the determination of the WaterRetention Value (WRV), the determination of the Salt Water RetentionValue (SRV), and the determination of the solubility in 1 percent NaCl.Determinations of these characteristics of bibulous and comparativefibers as reported herein were made according to the followingprocedural methods.

The D5 of carboxymethyl cellulose is the number of carboxymethyl groupsper anhydroglucose unit of cellulose. The analytical method employedherein was authored by Karin Wilson and published in SvenskPapperstidning, 63, pp. 714-- IS (1960). This method has been acceptedas giving correct results for grades of carboxymethyl cellulose varyingwidely in D8 and purity. In this analytical method NaCMC is given aninitial treatment with I N HCl in order to destroy any carbonatespresent, and if the sample is other than NaCMC, it must be converted toNaCMC or the procedure must be modified. The I N HCl treatment isfollowed by neutralization of the remaining l-ICl with a I N aqueoussolution of sodium hydroxide. The purified NaCMC, or wet cross-linkedcarboxymethyl cellulose fibrous material, in the sample is then isolatedquantitatively by adding ethyl alcohol to result in a final alcoholconcentration of percent by volume. The carboxymethyl cellulose,precipitated from the 80 percent by volume ethyl alcohol solution, isthen washed free of NaCl, first with 80 percent by volume ethyl alcoholand then with percent by volume ethyl alcohol. The remaining precipitatesample, consisting of purified carboxymethyl cellulose, is subsequentlydried, weighed and ashed at 575 C. The sodium carbonate thus obtained istitrated to a methyl red end point with standard sulfuric acid. The DSis the calculated as fol lows:

A m H SO4 H2SO4 NaCMC The WRVs reported herein were determined by aprocedure in which samples of bibulous fibers weighing from about 0.05grams to about 0.30 grams are soaked in milliliters of water in acovered container for at least 16 hours at room temperature. In thisprocedure for the determination of absorbency, subsequent to the soakingperiod, the soaked bibulous fibers are collected on a filter, lightlysqueezed and then transferred to 80-mesh screen baskets which aresupported oneshalf inch above the bottom of metal centrifuge tubes. Thetubes are covered with plastic covers, and the samples are centrifugedat a relative centrifugal force of l,500 to 1,700 gravities for 20minutes. The centrifuged samples are removed rapidly from the scrcensbymeans of tweezers to tared weighing bottles and weighed. The weighedsamples are then dried to constant weight at l 10 C. and reweighed. TheWRV is calculated as follows:

WRV: X 100 Wt. salt solution retained SRV: dry wt. fibers (salt free)X100 SRV: m x 100 The procedure used for determining the solubility in 1percent NaCl employs a 0.2-O.3 gram sample of the bibulous fibers to betested. The sample is washed with 80 percent by volume methanol and with100 percent by volume methanol prior to drying the sample at 1 C. andweighing it in a tared weighing bottle. The weighed sample is thenwashed into a beaker and soaked for an extended period (overnight) in100 milliliters of aqueous solution containing 1 percent by weight ofsodium chloride. The soaked fibers are then collected on a tared sintered glass filter, weighed while wet, dried at 1 10 C. and weighed again.The calculation used to obtain the solubility in 1 percent NaCl is asfollows:

L--- J Y T 99 Percent insoluble= 100 Percent soluble 100 Percentinsoluble EXAMPLE I Eighteen hundred and sixty-five grams of sheetedpurified wood pulp were steeped in a steeping press in 25 liters ofaqueous sodium hydroxide solution containing 8 percent by weight ofsodium hydroxide at room temperature for a period of 45 minutes. Thesteeped sheets were then pressed to a press weight ratio of alkalicellulose weight to weight of air dry cellulose (PWR) of 2.5, and thepressed sheets were shredded in a Baker-Perkins sigma blade shredder atroom temperature for a period of 45 minutes. After shredding the alkalicellulose in the Baker-Perkins sigma blade shredder, 56.5 grams ofepichlorohydrin were added to the shredded alkali cellulose in theshredder, and shredding was continued for an additional 45 minutes. Thefibrous alkali cellulose, with epichlorohydrin thoroughly dispersedthroughout, was then sealed in a plastic bag and remained therein for 18hours at 25 C. The resulting wet cross-linked cellulose fibers were thendispersed in water, neutralized with acetic acid, washed with water andcentrifuged. The wet cross-linked cellulose fibers were then dried andfound to be essentially insoluble in cadoxen and other solvents forcellulose. A sample of these wet cross-linked cellulose fibers was takenas illustration 2.

Three hundred and one grams (dry basis) of the dried crosslinkedcellulose prepared above were thereafter slurried in 13.4 liters of2-propanol and 1,602 milliliters of water in a 22- liter round-bottomedflask equipped with a mechanical stirrer. The resulting slurry wasstirred and heated until the temperature reached 40 C. When the slurrytemperature reached 40 C., 104.5 grams of sodium hydroxide dissolved in204 grams of water were added to the mixture in the 22-liter flaskduring a period of 10 minutes. The heating and stirring were continuedfor 30 minutes while the temperature of the mixture was increased to 60C At this time a solution of 1 12.5 grams of monochloroacetic acid in600 milliliters of 2-propanol was added to the 22liter flask, and theresulting final reaction mixture was stirred at 70 C. for a period of 4hours.

The reaction mixture was then cooled and neutralized with acetic acid,and the fibrous product was collected by deposition on a screen. The wetcross-linked carboxymethyl cellulose fibers, collected on the screen asbibulous fibers, were washed with 76 percent by weight (80/20 vol/vol)aqueous methanol. The washed wet crosslinked carboxymethyl cellulosefibers were then transferred to percent methanol and dried therefrom.The resulting bibulous fibers were tested according to the methods anddeterminations detailed above, and were determined to have a DS of 0.47,an SRV of 590, a WRV of 1,650 and a solubility (1 percent NaCl) of 5.7percent. The essentially water-insoluble cross-linked carboxymethylcellulose fiber product was found to be highly absorbent and wasjudgedsuitable for inclusion in the fibrous structure of absorbent surgicaldressings, catamenial napkins, tampons and bandage pads.

Additional examples of essentially water-insoluble crosslinked modifiedcellulosic fibers were prepared by using the cross-linking and singlestage etherification procedure of example l with the exception that theamounts of etherifying and cross-linking agent were varied to result inhigher and lower DS and cross-linking; these samples had thecharacteristics given in table 1 below. Table 1 also indicates the levelof crosslinking by the amount of epichlorohydrin added. The fibers oflllustration 1 are wood pulp fibers without either etherification or wetcross-linking, while the fibers of illustration 3 are wet cross-linked,low DS wood pulp fibers.

TABLE I Solubility Epiehloro- 1% NaCl hydrin I) S S RV W RV (percent)reacted Example:

I 0. 47 590 1, 650 5. 7 3. 0 0. 74 1, 2, 490 13. 0 3. 0 0. 40 570 920 6.0 6. 7 0. 36 415 1, 235 4. 4 3. 3 0. 58 765 1, 610 8.11 3. 3 0. 07 1,2653, 310 1G. 2 3. 3 0. 64 1,160 2, 465 14. 8 3. 3 l). 71 765 1, 250 X. 75. U

(I H7 H7 0 U l) 103 103 ll 0 l), 14 1X1] 21111 1, 0 3. t)

1 Percent by welght on cellulose.

The bibulous fibers of examples l -Vlll were highly absorbent withrespect to aqueous solutions. including physiological solutions andblood, and wcrejudgcd highly suitable for inclusion in fibrous structureof absorbent surgical dressings, catamenial napkins, tampons and bandagepads.

EXAMPLE 1X Eighteen hundred and sixty-five grams of sheeted purifiedwood pulp were steeped in a steeping press in 25 liters of 8 percent byweight sodium hydroxide at room temperature for 45 minutes. The steepedsheets were then pressed to a press weight ratio of alkali celluloseweight to weight of air dry wood pulp sheets (PWR) of 2.5, and thepressed sheets were shredded in a BakePPerkins sigma blade shredder atroom temperature for a period of 45 minutes. After shredding the alkalicellulose in the Baker-Perkins sigma blade shredder, 56.5 grams ofepichlorohydrin (3 percent epichlorohydrin on cellulose) were added tothe shredded alkali cellulose remaining in the shredded, and shreddingwas continued for an additional 45 minutes. The fibrous alkalicellulose, epichlorohydrin thoroughly dispersed throughout, was thensealed in a plastic bag and remained therein for 18 hours at I 25 C. Theresulting wet cross-linked cellulose fibers were then dispersed inwater, neutralized with acetic acid, washed with water and centrifuged.The wet cross-linked cellulose fibers were then dried and found to beessentially insoluble in cadoxen and other solvents for cellulose.

Three hundred and nine grams (dry basis) of the dried cross-linkedcellulose prepared above were thereafter slurried in 13,515 millilitersof 2-propanol and 1,654 milliliters of water in a 22-literround-bottomed flask equipped with a mechanical stirrer. The resultingslurry was stirred and heated until the temperature reached 40 C. Whenthe slurry tem' perature reached 40 C., 144 grams of sodium hydroxide in169 grams of water were added to the heated slurry during a period ofminutes. The heating and stirring were continued for 30 minutes whilethe temperature of the mixture was in creased to 65 C. At this time asolution of 155 grams of monochloroacetic acid in 485 milliliters ofZ-propanol was then added to the heated mixture in the 22 liter flask,and the temperature of the heated mixture was increased to 72 C. for 1hour. The slurry was thereafter allowed to cool to 56 C. over a periodof 2 hours.

At the end of the 2 hour cooling period an additional 65.6 grams ofsodium hydroxide in 81 grams of water was added to the stirred andcooled mixture, and stirring was continued at 56 C. for 30 minutes. Atthis time 775 grams of monochloroacetic acid in 245 milliliters of2-propanol was added to the stirred mixture, and stirring was continuedwith additional heating to increase the temperature of the slurry to69-72 C. duringa period of3 hours.

The slurry was then brought to a neutral pH by the addition of aceticacid, and the resulting wet cross-linked carboxymethyl cellulose fiberswere then collected on a screen. The collected bibulous fibers werewashed with 76 percent by weight aqueous methanol (80/20 alcohol/water,vol/vol) solution. The washed bibulous fibers were then transferred to100 percent methanol and dried therefrom.

The dried cross-linked bibulous fibers were tested according to themethod detailed above, and were determined to have a D5 of 0.90, an SRVof 1,460, a WRV of 3030 and a solubility (1 percent NaCl) of 16.1percent. The bibulous fibers of example IX, judged on the basis of theabove test procedures, were highly suitable for inclusion into fibermixtures intended for use in tampons, surgical dressings and absorbentpads.

Additional examples of bibulous fibers were prepared by the two-stageetherification procedure of example [X at higher and lower 05: andcross-linking by regulating the amounts of cross-linking andetherification agents employed. These samples had the characteristicsgiven in table 11 below.

with

TABLE II S0lu bility Epichloro- 1?} NaCl liydrin 11S SRV \l' RY(percent) reacted 1 Percent by weight on cellulose.

The wet cross-linked modified cellulosic fibers of examples lX-XVl havea higher DS than achieved with a single stage of etherification inexamples l-Vlll, and it is noted that the SRV and WRV values for thehigher DS wet cross-linked modified celluloses also tend to beincreased. The wet cross-linked modified cellulosic fibers of examplesIXXV[ were found, like the wet cross-linked modified celluloses ofexamples l- Vlll to be highly absorbent for aqueous solutions, includingphysiological solutions and blood, and were judged to be highly suitablefor inclusion in the fibrous structure of absorbent surgical dressings,catamenial napkins, tampons, bandage pads and articles of like use. Thesubstitution of potassium, lithium or ammonium salts of fibrouscarboxymethyl cellulose in the preparation of the bibulous fibers ofexamples l-XVI and other bibulous fibers will result in fibers withsimilar characteristics.

EXAMPLE XVII Thirty-two and two-tenths grams of purified wood pulpfibers were suspended in 1,428 milliliters of 2-propanol and 164milliliters of water in a 2-liter round-bottomed flask and stirredtogether while the solution temperature was increased to 44 C. Seventeenand five-tenths grams of sodium hydroxide in 31 milliliters of waterwere then added to the stirred mixture over a period of 10 minutes. Theresulting fibrous slurry was stirred for 30 minutes during which timethe slurry temperature was gradually raised to 65 C. After the 30-minute stirring period a solution of 18.8 grams of monochloroacetic acidin 67.5 milliliters of 2-propanol was added to the slurry. Thetemperature of the solution was then increased to 71-74 C., and theresulting slurry reaction mixture was stirred for 3 hours. After theShow reaction period a small sample of the fibrous CMC was collected byscreening, neutralized with acetic acid and washed with a 76 percent byweight aqueous methanol (80/20 alcohol/water, vol/vol) solution. At thispoint the fibrous carboxymethyl cellulose product was soluble in waterand had a D5 of 0.68, although it was maintained in fibrous form in thealcohol solution.

While the fibrous water-soluble carboxymethyl cellulose remained inslurry suspension, 3.9 grams of epichlorohydrin were added to thereaction mixture and the fibrous slurry was stirred for an additional3.5 hours at 72 C.

The resulting wet cross-linked carboxymethyl cellulose fibers werecollected on a screen, neutralized with acetic acid, washed with 76percent by weight methanol and thereafter dried from percent methanol.The bibulous fiber product of this example XVII was determined to have aD8 of 0.69, SRV of 1340, a WRV of 3,550 and a solubility (1 percentNaCl) of 19.6 percent. The bibulous fibers as shown by the test resultswere highly absorbent, with particular regard to their affinity forphysiological solutions, and were eminently suitable for inclusion intampons and surgical dressings.

EXAMPLE XVIII Thirty-two and two-tenths grams of wood pulp fibers wereslurried in 1,428 milliliters of 2-propanol and 164 milliliters of watercontained in a 2-liter round-bottomed flask equipped with a mechanicalstirrer. The fibrous slurry was stirred while raising the solutiontemperature to 44 C. Seventeen and fivetenths grams of aqueous sodiumhydroxide in 31 milliliters of water were added to the stirred mixtureover a l-minute period. The resulting mixture was stirred for 30 minutesduring which time the solution temperature was gradually raised to 65 C.After the 30-minute stirring period, a solution of 18.8 grams ofmonochloroacetic acid in 67.5 milliliters of 2- propanol was added tothe solution. Five minutes after the addition of the monochloroaccticacid in the solution, 3.9 grams of epichlorohydrin were added, and thetemperature of the solution was increased to 7 l74 C. while theresulting reaction mixture was stirred for 3.5 hours.

The resulting cross-linked modified cellulosic fibers were collected ona screen, neutralized with acetic acid, washed with 76 percent by weightmethanol and thereafter dried from 100 percent methanol. The bibulousfiber product was determined to have a D8 of 0.7 l an SRV of 1,265 a WRVof 2,950

g and a solubility (1 percent NaCl) of 14.1 percent.

The bibulous fibers of example XVlll were highly absorbent andhydrophilic in nature and were suitable for fibers for use in fibrousstructures such as surgical dressings, tampons, catamenial napkins, etc.where absorbency for aqueous and physiological solutions is a desirablefactor.

EXAMPLE XIX In order to ascertain the effectiveness of the presentbibulous fibers when included in effective amounts in catamenialdressings of the tampon type, test tampons were made including amountsof the presently. disclosed fibers. The tampons were constructed fromrayon staple fiber mats having a basis weight of about 2.5 ounces persquare yard. The rayon staple fiber mat was in the form of garnetted,cross-lapped needlepunched matting prepared from crimpcd rayon staplefibers having a denier of 3 and a length of 19/16 inches.

The bibulous fibers of the present invention were in individual fibrousform, having been run through an attrition mill and sifted through al4-mesh Rotap screen to break up fiber clumps.

The test tampons were prepared by cutting squares of the rayon mat to adimension of 10 inches X 10 inches. A rayon mat-bibulous fiber stack wasthen developed by laying down a 10 inch X 10 inch square of'the rayonmat and sifting 1.5 grams of the bibulous fibers uniformly thereonthrough a 14- mesh Rotap screen. After sifting the 1.5 grams of bibulousfibers on the rayon mat, another 10 inch X 10 inch square of rayon matwas laid on top of the sifted bibulous fibers, and another 1.5 grams ofbibulous fibers were sifted onto the new rayon mat.

This procedure was repeated until there were four layers each of rayonmat and bibulous fibers. At this point the stackwas capped with yetanother square of rayon mat to form a pad containing five layers ofrayon mat and four layers of sifted bibulous fibers. The so-formed pador stack was calendered to imbed the bibulous fibers into the rayonmatting, thus preventing a subsequent loss of bibulous fibers inprocessing.

Having preformed the rayon mat, bibulous fiber pad, individualrectangular tampon swatches having a dimension of 6 inches by 1% incheswere cut from the pad. Each so-cut tampon swatches weighed about 3.25grams. Each rayon layer in the tampon swatches weighed about 0.55 grams,and each bibulous fiber layer weighed about 0.125 grams. The percent ofwet cross-linked carboxymethyl cellulose fibers in each cut tamponswatch was approximately 15 percent.

The tampon swatches were then further formed into finished tampons byattaching a withdrawal string to the middle of the tampon swatch andthen folding over the cut tampon swatch to a 3-inch length. At thispoint in tampon preparation, the test swatches were conditioned to amoisture content of about 18 percent, and the final swatch weight beforedie pressing about 3.5 grams. The so-formed and folded tampon swatchescomprising prefonned fibrous bodies were compressed in a cylindricaldie, and the sides of the tampons were roughened or abraded by rollingthe tampons between two strips of card clothing, spaced 0.5 inchesapart. The finished length of the tampons was approximately 1.80 inchesand the diameter was approximately 0.45 inches. Comparative tampons wereformed in the described manner from rayon alone, i.e., from five layersof rayon fiber mat, and from rayon and bibulous fibers.

The test tampons were placed for testing within the confines of aballoonlike rubber membrane fixed inside a glass jacket. The tamponswere positioned so that about one-quarter inch of their proximal orinternal ends were lying on top of a hypodermic needle which waspositioned in the bottom of the rubber membrane and through which testfluid was emitted to the test sample in the artificial vagina formed bythe rubber membrane. The distal end of the tampons, or the end withwithdrawal string attached, was then about 2.5 inches from theartificial vagina opening and the withdrawal string extended outwardlythrough the opening. The test fluid had the following composition:

TABLE III Weight; Material: percent NaCl 1. 0

Na CO 0. 4 Glycerine 10. 0 NaCMC 0. 46 Distilled water 88. 14

Total 100. 00

This fluid is considered equal in average viscosity and solids contentto menstrual and other physiological fluids.

In testing, water was admitted into the glass jacket to a hydrostaticpressure of 6 inches. The rubber membrane was thus collapsed and formedinto a tight-fitting sheath around the test tampon. The test fluid wasthen admitted through the hypodermic needle at a rate which varied fromabout 1 mil- TABLE IV Test tampon Total absorb- Absorp- Weight ency tioneflfi- Fiber description (grams) (grams) ciency l rayon matting 3. 47 154. 3 Rayon matting, 15% by weight of Example XIV bibulous fibers 3. 5020 5. 9 Rayon matting, 15% by weight of Example VII bibulous fibers t 3.58 22 6. 2

1 Grams test fluid absorbed/gram of tampon weight.

The data of table lV show that the test tampons containing bibulousfibers in an amount equal to about 15 percent of their weight were atleast 37 percent more effective in total absorbency than the comparativetest tampon not containing bibulous fibers. The inclusion of additionalweight percentages of bibulous fibers will increase the total absorbencyof such test products, but it is considered that the inclusion of 15percent by weight bibulous fibers is sufficient to result in a tamponproduct which exhibits substantially more total absorbency than productspresently available on the market and is characterized by a considerablyreduced failure rate. Tampon failure is defined herein as failure tocontain menstrual flow during use.

EXAMPLE XX In order to ascertain the effectiveness of the presentbibulous fibers when used in surgical dressings, catamenial napkins andabsorbent pads, a 0.5 gram sample of the bibulous fibers of thisinvention, choosing specifically the bibulous fibers of example XI, wereformed into an 2 inch X 2 inch absorbent pad. The bibulous fibers in thepad exhibited a D5 of 0.79. an SRV of l370, a WRV of 3480 and asolubility in l percent by weight aqueous NaCl of 16.6 percent.

The 2 inch X 2 inch absorbent pad of bibulous fibers was completelysaturated with whole human blood by adding blood dropwisc until excessblood flowed from the pad. The excess blood in the saturated pad waspressed out under a pressure of 1 pound per square-inch on the fiber padduring a 3-minute period between blottcrs, The blotters were changed, topresent fresh blotting surfaces, as they took up the excess blood in thepad. The weight of blood retained in the pad per gram of air drybibulous fiber was calculated. The pad of this example IX formed ofbibulous fibers retained 9.3 grams of blood per gram of bibulous fiber.Table V below compares the blood retention of the bibulous fibers ofthis example X] with othenfibers commonly used in absorbent pads andtested by the procedure of this example:

TABLE v 1 Gram blood/grain fiber.

As shown by the blood retention results given in table V above, thebibulous fibers of example X1 exhibited better than three times theblood retention capacity of the best of the other commonly employedfibers tested. When other bibulous fibers are prepared according to thepresent disclosure and' tested for the retention of blood, menstrualfluids, 1 percent by weight aqueous salt solutions and otherphysiological solutions and for the retention of water, similarlyenhanced and improved results will be obtained.

EXAMPLE XXI In order to ascertain the effectiveness of the present bibulous fibers in absorbing and retaining undissolved water fromsubstantially immiscible aqueous systems comprised of water togetherwith at least one hydrocarbon, 7 grams of the bibulous fibers of examplell were packed into a cylinder having an inside diameter of 2 inches anda height of 7 inches. Three and one-half liters of gasoline containing,as entrained fluid, 50 grams of water per liter of gasoline was passedthrough the cylinder. The gasoline passed through the cylinder while thewater was absorbed and remained therein, as evidenced by a water contentof 0.01 percent by weight in the gasoline passing though the cylinder.Similar results are obtained in substantially immiscible aqueous systemscontaining chloroform, toluene, benzene, xylene, kerosene, pentane, hexane and cyclohexane. Also systems containing mixtures of theaforementioned solvents, for example l liter of chloroform together with2.5 liters of hexane, and 175 grams of water, are

found to be amenable to water removal according to the procedure ofexample XXI. ln certain instances flow rates were improved by combiningthe bibulous fibers with glass and other inert carrier fibers accordingto conventional dispersive practice in the formation of filter pads.

Since many apparent and widely different embodiments of the bibulousfibers of this invention can be made in physical form, chemicalcomposition and use without departure from the spirit and scope of theinvention, it will be understood that the invention is not limited tothe herein disclosed specific embodiments thereof, except as defined inthe appended claims.

Having thus described the invention, what we claim is:

l. Substantially water-insoluble, wet cross-linked carboxymethylcellulose fibers, having a WRV of about 900 to about 3,400 and a SRV ofabout 400 to about 1,500 and manifesting their native cellulosic fiberstructure, for use in fibrous structures for the absorption andretention of aqueous solutions, which substantially water-insoluble, wetcross-linked fibers of carboxymethyl cellulose have a degree ofsubstitution of about 0.4 to about 1.6.

2. Substantially water-insoluble, epichlorohydrin wet crosslinkedcarboxymethyl cellulose fibers, having a WRV of about 900 to about 3,400and a SRV of about 400 to about 1,500 and manifesting their nativecellulosic fiber structure, for use in fibrous structures for theabsorption of aqueous solutions, which substantially water-insoluble,epichlorohydrin wet cross-linked fibers of carboxymethyl cellulose havea degree of substitution of about 0.4 to about 1.6.

3. An absorbent fibrous structure, comprising a preformed absorbent pad,containing in effective amount the substantially water-insolublecarboxymethyl cellulose fibers of claim 2.

4. The absorbent fibrous structure of claim 3 which is a surgicaldressing.

5. The absorbent fibrous structure of claim 3 which is a catamenialnapkin.

6. Theabsorbent fibrous structure of claim 3 which is a diaper.

7. The absorbent fibrous structure ofclaim 3 which is a tampon.

8. The absorbent fibrous structure of claim 3 which is a filter forremoving undissolved water from substantially immiscible aqueous systemscomprised of water together with at least one hydrocarbon.

9. Substantially water-insoluble, wet cross'linked sodium carboxymethylcellulose fibers, having a WRV of about 1,100 to about 3,400 and a SRVof about 400 to about 1,500 and manifesting their native cellulosicfiber structure, for use in fibrous structures for the absorption ofphysiological solutions, which substantially water-insoluble, wetcross-linked fibers of sodium carboxymethyl cellulose have a degree ofsubstitution of about 0.6 to about 1.2.

10. A tampon, comprising a preformed fibrous body compressed incylindrical form, containing in effective amount the substantiallywater-insoluble, wet cross-linked sodium carboxymethyl cellulose fibersof claim

1. Substantially water-insoluble, wet cross-linked carboxymethylcellulose fibers, having a WRV of about 900 to about 3,400 and a SRV ofabout 400 to about 1,500 and manifesting their native cellulosic fiberstructure, for use in fibrous structures for the absorption andretention of aqueous solutions, which substantially water-insoluble, wetcross-linked fibers of carboxymethyl cellulose have a degree ofsubstitution of about 0.4 to about 1.6.
 2. Substantiallywater-insoluble, epichlorohydrin wet cross-linked carboxymethylcellulose fibers, having a WRV of about 900 to about 3,400 and a SRV ofabout 400 to about 1,500 and manifesting their native cellulosic fiberstructure, for use in fibrous structures for the absorption of aqueoussolutions, which substantially water-insoluble, epichlorohydrin wetcross-linked fibers of carboxymethyl cellulose have a degree ofsubstitution of about 0.4 to about 1.6.
 3. An absorbent fibrousstructure, comprising a preformed absorbent pad, containing in effectiveamount the substantially water-insoluble carboxymethyl cellulose fibersof claim
 2. 4. The absorbent fibrous structure of claim 3 which is asurgical dressing.
 5. The absorbent fibrous structure of claim 3 whichis a catamenial napkin.
 6. The absorbent fibrous structure of claim 3which is a diaper.
 7. The absorbent fibrous structure of claim 3 whichis a tampon.
 8. The absorbent fibrous structure of claim 3 which is afilter for removing undissolved water from substantially immiscibleaqueous systems comprised of water together with at least onehydrocarbon.
 9. Substantially water-insoluble, wet cross-linked sodiumcarboxymethyl cellulose fibers, having a WRV of about 1,100 to about3,400 and a SRV of about 400 to about 1,500 and manifesting their nativecellulosic fiber structure, for use in fibrous structures for theabsorption of physiological solutions, which substantiallywater-insoluble, wet cross-linked fibers of sodium carboxymethylcellulose have a degree of substitution of about 0.6 to about 1.2.
 10. Atampon, comprising a preformed fibrous body compressed in cylindricalform, containing in effective amount the substantially water-insoluble,wet cross-linked sodium carboxymethyl cellulose fibers of claim 9.